This is the first systematic and truly methodical study of de Kooning's idiosyncratic working methods and use of materials. This in-depth study of the paintings of Willem de Kooning (1904-1997), Dutch-born American abstract expressionist painter, from the 1940s through the 1970s breaks new ground in its analysis of the artist's working methods and yields new information about previously unreported materials. De Kooning's idiosyncratic working methods have long provoked intense speculation and debate among conservators and art historians, primarily on the basis of visual inspection and anecdotal accounts rather than rigorous technical analysis. This is the first methodical study of de Kooning's creative process to use comprehensive scientific examinations of the artist's pigments, binders, and supports, to inform art historical interpretations, thereby presenting a key to the complicated evolution of the artist's work.